Berlin 2005 – wissenschaftliches Programm
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A: Atomphysik
A 11: Ion-Atom/Molecule Collisions, Exotic Atoms
A 11.4: Fachvortrag
Montag, 7. März 2005, 17:15–17:30, HU 3075
Evaporation of negative ions out of a 22-pole ion trap — •J. Mikosch1,2, U. Frühling2, M. Weidemüller2, D. Schwalm1 und R. Wester2 — 1Max-Planck-Institut für Kernphysik, 69117 Heidelberg — 2Physikalisches Institut, Universität Freiburg, 79104 Freiburg
Ion traps with controllable temperature offer a ideal environment for reactions of molecular ions with neutral buffer gas molecules. In our experiment a multipole RF ion trap is used as a source for state-selected ions for a crossed beam experiment.
In this work we have studied the storage conditions in this trap with Cl− anions. These are selected from a supersonic expansion ion source via time of flight and analyzed after storage with a second time of flight detector. We achieve storing conditions, where there are practically no reactive collisions taking place in the trap. This enables us to investigate trap losses dominated by elastic collisions of the ions with the buffer gas and by interactions among the ions themselves. We have studied the dependence of the evaporation rate on buffer gas density, temperature and trap depth. These results are compared with models of the evaporation process.